Results of more than 11,000 scans with weightbearing CT : impact on costs, radiation exposure, and procedure time

Background: Weightbearing CT (WBCT) has been proven to more precisely measure bone position than conventional weightbearing radiographic series (R) and conventional CT (CT). The purpose of this study was to assess the benefit of using WBCT instead of R and/or CT as the standard imaging modality, evaluating image acquisition time, radiation dose, and cost-effectiveness. Methods: All patients who obtained a WBCT as part of standard of care from July 1, 2013 until March 15, 2019 were included in the study. Image acquisition time (T), radiation dose (RD) per patient, and costeffectiveness were analyzed and compared between the time period using WBCT (yearly average) and the parameters from 2012, i.e. before the availability of WBCT (RCT group). Results: 11,009 WBCT scans were obtained from 4987 patients (4,987 scans (45%) before treatment; 6,022 scans (55%) at follow-up). On a yearly average, 1,957 WBCTs (bilateral scans) and an additional 10.6 CTs (bilateral feet and ankles) were obtained (WBCT group). In 2012, 1,850 Rs (bilateral feet, dorsoplantar and lateral, metatarsal head skyline view) and 254 CTs were obtained from 885 patients (RCT group). The mean yearly RD was 4.3/4.8uSv for the WBCT/RCT groups (mean difference of .5 uSv; a decrease of 10% for the WBCT group; p < .01). Yearly mean T was 114/493 h in total (3.3/16.0 min per patient) for WBCT/RCT groups (mean difference of 379 h; a 77% decrease for the WBCT group; p < .01). Yearly cost-effectiveness was a mean profit of 43,959/-723 Euros for WBCT/RCT groups. Conclusions: 11,009 WBCT scans from 4,987 patients over a period of 5.6 years at a foot and ankle department resulted in 10% decreased RD, 77% decreased T, and increased financial profit (51 Euros per patient) for the institution. (c) 2019 The Author(s). Published by Elsevier Ltd on behalf of European Foot and Ankle Society

Weight-bearing cone beam CT scans in the foot and ankle

The 3D anatomical complexity of the foot and ankle and the importance of weight-bearing in diagnosis have required the combination of conventional radiographs and medical CT. Conventional plain radiographs (XR) have demonstrated substantial limitations such as perspective, rotational and fan distortion, as well as poor reproducibility of radiographic installations. Conventional CT produces high levels of radiation exposure and does not offer weight-bearing capabilities. The literature investigating biometrics based on 2D XR has inherent limitations due to the technology itself and thereby can focus only on whether measurements are reproducible, when the real question is whether the radiographs are. Low dose weight-bearing cone beam CT (WBCT) combines 3D and weight-bearing as well as 'built in' reliability validated through industry-standardized processes during production and clinical use (quality assurance testing). Research is accumulating to validate measurements based on traditional 2D techniques, and new 3D biometrics are being described and tested. Time- and cost-efficient use in medical imaging will require the use of automatic measurements. Merging WBCT and clinical data will offer new perspectives in terms of research with the help of modern data analysis techniques

Osteotomies around the knee alter alignment of the ankle and hindfoot: a systematic review of biomechanical and clinical studies

Purpose: Emerging reports suggest an important involvement of the ankle/hindfoot alignment in the outcome of knee osteotomy; however, a comprehensive overview is currently not available. Therefore, we systematically reviewed all studies investigating biomechanical and clinical outcomes related to the ankle/hindfoot following knee osteotomies. Methods: A systematic literature search was conducted on PubMed, Web of Science, EMBASE and Cochrane Library according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered on international prospective register of systematic reviews (PROSPERO) (CRD42021277189). Combining knee osteotomy and ankle/hindfoot alignment, all biomechanical and clinical studies were included. Studies investigating knee osteotomy in conjunction with total knee arthroplasty and case reports were excluded. The QUality Appraisal for Cadaveric Studies (QUACS) scale and Methodological Index for Non-Randomized Studies (MINORS) scores were used for quality assessment. Results: Out of 3554 hits, 18 studies were confirmed eligible, including 770 subjects. The minority of studies (n = 3) assessed both high tibial- and distal femoral osteotomy. Following knee osteotomy, the mean tibiotalar contact pressure decreased (n = 4) except in the presence of a rigid subtalar joint (n = 1) or a talar tilt deformity (n = 1). Patient symptoms and/or radiographic alignment at the level of the ankle/hindfoot improved after knee osteotomy (n = 13). However, factors interfering with an optimal outcome were a small preoperative lateral distal tibia angle, a small hip–knee–ankle axis (HKA) angle, a large HKA correction (>14.5°) and a preexistent hindfoot deformity (>15.9°). Conclusions: Osteotomies to correct knee deformity alter biomechanical and clinical outcomes at the level of the ankle/hindfoot. In general, these changes were beneficial, but several parameters were identified in association with deterioration of ankle/hindfoot symptoms following knee osteotomy

Mechanical stress in the hindfoot : quantification of inflammatory responses and structural deformity

An intimate relation has been exposed between the function of the Achilles tendon and an altered position of the hindfoot in former anatomical, biomechanical and clinical studies. However, the underlying mechanisms evoking Achilles tendon disorders and their interaction with hindfoot deformity remain elusive. This can be attributed to fundamental flaws in current investigational techniques, which hamper a quantitative analysis of inflammatory cell types in Achilles tendinopathy and an accurate assessment of hindfoot alignment. Moreover, recent research identified mechanical stress as pivotal component in the pathogenesis of both conditions, as summarized in Chapter 1.4 and 1.5. Therefore, we implemented a flow cytometer to characterize cellular responses in patients with chronically overloaded mid-portion Achilles tendinopathy and a weightbearing CT to determine the three-dimensional hindfoot alignment. The general rationale behind this work is to improve the aforementioned shortcomings in the investigational modalities associated with Achilles tendinopathy and hindfoot deformity, in order to enhance further research focussed on the interlinkage between both conditions. In chapter 3.1, surgical samples were obtained from patients with chronically overloaded mid-portion Achilles tendinopathy resistant to conservative therapy. A flowcytometer was used to analyse distinct inflammatory cell populations in tendinopathic samples compared to a control population with underload Achilles tendon as a consequence of hemi-plegia. In chapter 3.2, weightbearing CT images of the hindfoot were analysed. Measurement methods from plain radiographs were implemented on plain radiographs and the observer agreement was assessed to determine a reliable measurement method in section 3.2.1. Subsequently, we established reference values for normal hindfoot alignment in section 3.2.3. As our measurement method was reliant on the longitudinal axis of the tibia, we questioned to what extend hindfoot deformity was associated with lower limb alignment in section 3.2.4. Once we gathered these insights concerning two-dimensional measurements in the hindfoot, we raised the bar and performed a transition towards their three-dimensional equivalents in section 3.3.5. This methodology was subsequently implemented in assessing three-dimensional alignment after surgical correction of hindfoot deformity, in section section 3.3.6. We revealed distinct inflammatory cell populations present in Achillestendinopathy compared to a control population, in chapter 3.1. These were mainly situated in the monocyte population and to a lesser extend in a subgroup of lymphocytes, the γδ T-cells . We translated former radiographic measurements to a two-dimensional and subsequent three-dimensional assessment of hindfoot deformities in chapter 3.2 The highest reliability to determine hindfoot alignment on weightbearing CT was found in section 3.2.1 for the measurement method using the intersection of the longitudinal axis of the tibia and axes connecting the inferior point of the calcaneus with the center of the talar dome. We found a mean hindfoot valgus alignment of 0.79° ± 3.2 in a cohort of subjects with a normal hindfoot alignment in section 3.2.2. In respect the lower limb alignment we found an association between hindfoot varus and knees valgus and between hindfoot valgus and knee varus, a converse pattern in patients without ankle osteoarthritis in section 3.3.3. The two-dimensional measurements differed significantly in section 3.3.5 from the three-dimensionional measurements and a higher reliability in favor of the three-dimensional measurements was demonstrated. In the final section 3.3.6 we used the established three-dimensional measurements to assess surgical correction of hindfoot deformity and found an improvement of the hindfoot alignment and could detect several rotations induced by the osteotomy which were previously not detectable on standard imaging. This work pioneered in characterizing inflammatory cell populations using a flowcytometer in Achilles tendinopathy and by translating former two-dimensional measurements in hindfoot deformities to three-dimensional equivalents using a weightbearing CT. This required a multidisciplinary collaboration with high-end immunologists and engineers to overcome different hurdles associated with former protocols of both flowcytometry and weightbearing CT. Our innovative approach succeeded in improving both protocols, which are able to enhance the present research focussed on the interlinkage between Achillestendinopathy and hindfoot deformity. For these reasons, our work is a gamechanger in both fields and paves the road for different future perspectives. These could be aimed at unravelling the mechanosensitive pathways provoking inflammatory cell populations in Achillestendinopathy, which would enable potential targets for focal immunomodulating therapy. In addition, the role of corrective treatments on different magnitudes of hindfoot deformity could be assessed both statically and dynamically to identify their attributive role in the therapeutic strategies for Achilles tendinopathy